Morpho-physiological traits, antioxidant capacity, and nitrogen metabolism in ramie under nitrogen fertilizer

Optimum fertilization is one of the challenges to agricultural sustainability. Understanding the physiological and biochemical response of plants to available nutrients is important for optimization of crop management practices. Present study investigated the effects of different levels of N fertilizer (N-0 = 0 kg ha(-1) [Control], N-1 = 140 kg ha(-1) [Low], N-2 = 280 kg ha(-1) [Medium], and N-3 = 420 kg ha(-1) [High]) on growth, gaseous exchange, antioxidant capacity, and N metabolism in ramie (Boehmeria nivea L.) under greenhouse conditions in a completely randomized design (CRD) with three replications. Nitrogen application improved the plant growth, chlorophyll contents, and antioxidant activity of ramie; the maximum shoot fresh biomass (91 g), shoot dry biomass (13.7 g), number of leaves (46.5), and number of stems (6.4) were recorded at medium N rate. However, the growth was reduced under high N rate. Except for intercellular CO2 concentration, all the other gas exchange parameters were significantly affected by the N levels. Increasing N level improved the activities of nitrate reductase (NR), glutamine synthetase (GS), and glutamate synthase (GOGAT), and enhanced the chlorophyll and soluble protein contents in ramie leaves. Thus, N fertilizer at medium rate is relatively more effective in the growth of ramie and biomass production.